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Is National Differential GPS Lost?
Nealix writes, "This article at GPSWorld reports that National Differential GPS (NDGPS) is endangered in the 2007 budget. This has ramifications for a variety of government programs such as the Intelligent Transportation System and Positive Train Control by the Department of Transportation. Blind people and robots also benefit from highly accurate GPS navigational capability provided by NDGPS, which appears to work better in the urban canyons. If NDGPS loses, the winner would appear to be the FAA-backed Wide Area Augmentation Service (WAAS). Of course, what would be really cool is to see more GPS sites around the country make DGPS data (RTCM) available over the Internet."
Ah yes, of course GPS making use of DGPS data (RTCM) would be better than FAA-backed WAAS if NDGPS loses - everybody knows that. Now, BRB while I RTFA.
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Would not actually be hard. Technically you could do it yourself. Really at it takes is a fixed location GPS (calibrated) hooked up to a server which processes the NMEA data and uploads the correction dynamically.
the more they over-think the plumbing the easier it is to stop up the pipe
Circumcision is child abuse.
I didn't mind punch cards being phased out either....
Engineering is the art of compromise.
Why, again, should we be sorry that NDGPS is going away? It sounds like market forces at work here. The only specific instance that TFA mentions where NDGPS has an advantage is *some* in-building penetration. Why should we build out a *national* network for only some in-building penetration? It sounds to me that WAAS is getting funding because it is technically and economically the better solution. Why is this a problem?
I personally *hate* using the NDGPS (beacon) real-time corrections. We only have two reference stations in my state and neither are worth a damn in my city. I work as for a major GPS company, and though we do sell beacon receivers quite briskly, I hate using them.
I much prefer using WAAS for real-time, especially after the two new satellites are up and fully functional. I do post-process most of my data, however, so the CORS stations work just fine for my needs.
"Equal bytes for women!"
No.
DGPS can be far more precise than military precise setting. A resolution of one meter is more than good enough for any weapon system that would use GPS.
I remember hearing about a form of DGPS that has a lot higher resolution than one meter. It is often used for surveying.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
If NDGPS is indeed lost, can't we just use its GPS to find it?
The only thing I hate more than hypocrites are people who hate hypocrites.
WAAS is the next step in this technology. Let the dinosaur die and let's move on.
Now you're telling me that we can't afford to clip another $10 million off the Defense budget and give it to this service (which may, arguably, help the coast guard in defending our shores)? Come on, we spend way more on military than any other country. It's good to maintain military superiority but do we really need it when you look at that chart? The next highest is China with maybe an 1/8th as much spending as we do. Give me a break!
There's no way anyone can justify cutting the spending on this program given what we've invested in it and how useful it is. When you look at where the rest of our spending goes, $10 million is nothing. No one can complain that the cost versus potential utility of this thing isn't high enough.
My work here is dung.
DGPS does the correction on a satellite-by-satellite basis. The GPS receiver must support DGPS corrections, which are uploaded to the receiver to include in its internal calculations before the separate satellites are combined to form the final result.
Remember when GPS itself was thought to be in danger back in 2000? Remember when there was talk of balancing the budget? Read this article all the way from 1996 about the military importance of GPS technology. It's worth the read.
About the NDGPS vs. WAAS debate: I work for a group that relies heavily on GPS for aviation purposes. As the number of uses for GPS expand, as they inevitably will, new technologies will spring up. NDGPS vs. WAAS is like 802.11g vs 802.11a. I think they both have a place. If the government won't support NDGPS, perhaps there is a commercial application? What are the FCC regulations on the 300KHz spectrum? If no one will pay for it, let it die, I think.
Okay, <rant>
I laughed when I read, "Therefore, when it comes to cutting the budget during tight times, programs like NDGPS are prime targets." How are we cutting costs when we just ran up a record high deficit in the last two years? I like it that we're cutting costs. Let's cut some of the really big ones, like military spending!
</rant> Couldn't resist.
Think about the implications if WAAS (and soon-to-arrive LAAS) is decommissioned -- the FAA has already issued WAAS-based LPV approach plates for IFR ops. Switching to another system would cause a huge momentum change in a critical sector of the safe operation of our airways.
The FAA upset thousands of pilots when they pulled the plug on TIS (Traffic Information Service) when approach radars (ASR 9 to ASR11) were upgraded and their investment in TIS equipment was obviated -- the one they chose, ADS-B (Automatic Dependent Surveillance - Broadcast) provides more data and is more scalable. Essentially instead of using radars and transponder return codes to figure out who's who, let the aircraft broadcast their position s constantly without having to wait for a radara sweep. But I digress.
Same with these conflicting solutions -- one my be "better" in terms of feature set but the other has momentum. MP3 vs OGG anyone? Beta vs VHS?
I'd rather have a standard augmented data-channel and ground based "satellites" to allow my portable GPS to function in the skyscraper canyons and provide local traffic and business lookups so that I don't need to subscribe to CD/DVD updates when the data could just be real-time.
Precisely, Carrier Differential GPS can be on the order of less than 10 centimeters on a good day. The other factor is that CDGPS works off of precision epemeredies that are released the next day. Good for survey, not handy for weapons. (There is real time kinematic GPS with such precision but not much in the civilian world.)
That being said P code recievers make differential and carrier differential easier.
Please, when using terms like "national", make it clear which nation you're talking about.
The use of "GPS" and "WAAS" does make it clear. The FP did not say "GLONASS", or "EGNOS", or "GAGAN", or "MSAS", or even the generic term "SBAS".
The whole world can use GPS, but the US outright owns it and controls every aspect of its operation, whether the rest of the world likes it or not. Dubbya could order SA turned back on tomorrow, and all the foreign users that have come to critically require reasonably accurate GPS would have no say in the matter whatsoever.
On top of this, WAAS isn't the end of the line, there are more systems coming on-line that will improve GPS acuracy even more. The old system was OK for what it was, but the need for extra receivers by each user certainly limited it's adoption. It should be phased out.
And one thing I just have to comment on from the article and even the /. blurb: "Positive Train Control"! Are we really to believe we need taxpayer funded meter accuracy for GPS for train control? Do these trains really wander from from the tracks we know the location of? Isn't normal GPS accuracy just fine for choo-choo trains? And in the rare cases where higher accuracy might come in handy (although should hardly be needed), such as a switchyard, couldn't the location itself provide a small simple system for far less cost than asking the taxpayers to support it for this special use? You don't even need Internet data for this, you just have to agree on the location of the stationary differential receiver site and put a receiver without WASS there, it's error from it's known location is the same or better correction information than you could get from the Internet.
I'm an American. I love this country and the freedoms that we used to have.
There is no need for NDGPS. How WAAS works
Just to explain to the submitter if this is not already crystal clear: There is no need for NDGPS. WAAS has fortunaltely replaced it.
NDGPS required a seperate receiver to get the error signal from a ground based transmitter. You also had to be near a ground based error transmitter for this to work.
The ground based error transmitters are still there, and more are beeing added. Instead of transmitting locally, a database of errors over a wide area is constructed, and a geostationary sattelite transmits the error database on the same wavelenght as the other GPS sattelites to all GPS devices. All that is needed for this is typically a firmware update in the GPS unit.
Simple, effective, cheap.
"Fix it"
Oh, please. I think Libertarians are completely goofy, but this is just too easy. As long as you're a Libertarian who believes in initiation of force to protect intellectual property laws. Of which there are tons. Personally, I don't see how they wrap their heads around that without them exploding, but it works for them.
The problem, of course, is that the GPS broadcasts are a public good, so how do protect that, in order to charge for it? Encryption? If people get their hands on your device, they can break the encryption. It all boils down to giving a government enforced monopoly on using the broadcasts to the people who put the satellites up. Otherwise, the people putting up the satellites could never recoup their initial investments, as anyone could make a receiver and not have to pay the people putting them up.
But as I mentioned, plenty of Libertarians can quite easily wrap their heads around the paradox of enforced ownership of intellectual property. It all comes from a very flexible definition of "initiation of force." Basically, any use of force a libertarian doesn't like is "initiation of force," while anything else is "retaliatory force" which is, of course, justified as YOUR NATURAL RIGHT!
See, in order to troll successfully, you have to have an understanding, nay, even a love for that which you troll. You have to care enough about your subject to actually get inside and find out what makes 'em tick, what are their foibles, paradoxes and hot buttons.
So, any Libertarians out there want to respond to a self proclaimed troll and tell me how you would do it without intellectual property protections? I mean, if you thought protection of real property took a lot of state sponsored violence, imagine how much state sponsored violence is necessary for the protection of imaginary property? Come on, you guys are smart, I mean, it's not like you just memorize your party dogma and can't answer simple questions that fall outside the bounds of official, party sponsored reasoning, is it?
Happy Troll Tuesday!
P.S. As much as I think the vast majority of Libertarians are goofy, I've had conversations with some here who are probably smart enough to figure out how to do this, so even if no one responds, that doesn't mean all libertarians are dogma spouting mouth breathers who couldn't reason their way out of a paper bag. Some would manage to deduce that ripping open the bag was not in fact initiation of force, as the bag was depriving them of their natural right not to be in a paper bag.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
Because thats what my Garmin GPS uses. It (and I) have never heard of NDGPS so I hope WAAS doesn't get phased out. given that it also makes sennse to have a single standard, it makes sense to me for NDGPS to go away.
Three items of note:
1. Sky visibility can significantly degrade your accuracy via WAAS. Personally, working in a lot of areas with random overhead cover (trees) I prefer NDGPS to WAAS even if I have to download the corrections and post correct. In a test I ran in a suburban forested park NDGPS was able to meet the 1 Meter accuracy claims even with heavy overhead (40+ foot trees)in a comparison vs 6inch pixel aerial photography. WAAS consistantly got a ~2-5 meter error on the same locations.
2. NDGPS stations are already failing in our area. Of the Three stations that are barely within the range at which they are useful, none consistantly provide base station data via the internet, and 1 has failed completely. If the current funding level is approved ($0) I don't see any improvement in the near future. Thus my company has invested in our own DGPS base station to guartee 1 meter accuracy in the event of NDGPS unavailability, despite the downsides (maintenance, requires a survey accurate point to permenantly mount the basestation, basestation must run at least one hour before and after field collection of data to insure coverage).
3. In our current contract with a US government agency that specified 1 meter accuracy GPS, WAAS was not an acceptable correction option. So it was either rely on unreliable Government funded base stations, or buy our own. (BTW, I'm glad we did buy our own).